利用DynamicExpression.ParseLambda实现Eval

模拟实现,性能还不错，比DynamicInvoke性能好的多。

中间加了一次Convert，可以实现任何对象的属性的调用，也就是EvalEx.GetEval<Func<object, object>>方式

    public static class EvalEx

    {

        public static T GetEval<T>(Type type, string propertyPath)

        {

            if (type == null)

                return default(T);

            var func = DynamicExpression.ParseLambda(type, null, propertyPath);

            var objParameter = System.Linq.Expressions.Expression.Parameter(typeof(object), "obj");

            var objConvert = System.Linq.Expressions.Expression.Convert(objParameter, type);

            var objInvoke = System.Linq.Expressions.Expression.Invoke(func, objConvert);

            var resultExpression = System.Linq.Expressions.Expression.Lambda<T>(objInvoke, objParameter);

            return resultExpression.Compile();

        }

    }

        static void Main(string[] args)

        {

            var list = new List<TT>();

            for (int i = 0; i < 10000; i++)

            {

                list.Add(new TT() { T1 = i.ToString(), T3 = i });

            }

            Stopwatch sw = new Stopwatch();

            var do1 = EvalEx.GetEval<Func<TT, string>>(typeof(TT), "T1+ (T3*100).ToString() ");

            var do2 = EvalEx.GetEval<Func<object, string>>(typeof(TT), "T1+ (T3*100).ToString() ");

            var do3 = EvalEx.GetEval<Func<object, object>>(typeof(TT), "T1+(T3*100).ToString() ");

            sw.Start();

            list.ForEach(p => do1(p));

            Console.WriteLine(sw.Elapsed);

            sw.Restart();

            list.ForEach(p => do2(p));

            Console.WriteLine(sw.Elapsed);

            sw.Restart();

            list.ForEach(p => do3(p));

            Console.WriteLine(sw.Elapsed);

            sw.Restart();

            list.ForEach(p => do1.DynamicInvoke(p));

            Console.WriteLine(sw.Elapsed);

            sw.Stop();

            Console.Read();

        }